The invention relates to chip cards, and especially to chip cards comprising data elements stored in electrically erasable and programmable non-volatile memories (EEPROMs).
chip cards are increasingly being provided with this type of memory in order to contain:
either data for the customizing of the card (confidential code, data to identify the authorized application or the authorized user etc.), PA1 or data that may vary during the use of the card (credit in terms of prepaid units, electronic wallet data, data on transactions etc.), PA1 or again programs that can be executed by a microprocessor placed on the same integrated circuit chip, these programs being stored in the non-volatile memory so that they are not permanently fixed at the time of manufacture.
These EEPROMs are provided on the card along with other types of memories, namely random-access memories (RAMs) or read-only memories (ROMs).
For example, the following is a frequent use of EEPROMs: a microprocessor works essentially with programs stored in a read-only memory (ROM) but certain programs, called filters and placed in an EEPROM, can be used to modify the possibilities of the programs stored in a ROM, or more generally to modify the application of the card. These programs are placed in an electrically programmable memory so that they can be written in the card by electrical programming, after manufacture, according to the needs of the application or the user.
It has been observed, however, that there is a risk that the cards constituted in this way will not be entirely satisfactory in terms of longevity.